Add priority boosting for TREE_PREEMPT_RCU, similar to that forTINY_PREEMPT_RCU. This is enabled by the default-off RCU_BOOSTkernel parameter. The priority to which to boost preemptedRCU readers is controlled by the RCU_BOOST_PRIO kernel parameter(defaulting to real-time priority 1) and the time to wait beforeboosting the readers who are blocking a given grace period iscontrolled by the RCU_BOOST_DELAY kernel parameter (defaulting to500 milliseconds).

/* * Set the per-rcu_node kthread's affinity to cover all CPUs that are- * served by the rcu_node in question.+ * served by the rcu_node in question. The CPU hotplug lock is still+ * held, so the value of rnp->qsmaskinit will be stable. */ static void rcu_node_kthread_setaffinity(struct rcu_node *rnp) {@@ -1626,8 +1651,7 @@ static void rcu_node_kthread_setaffinity(struct rcu_node *rnp) int cpu; unsigned long mask = rnp->qsmaskinit;